二分法求函数零点

This is an R Markdown document. Markdown is a simple formatting syntax for authoring HTML, PDF, and MS Word documents. For more details on using R Markdown see http://rmarkdown.rstudio.com.

When you click the Knit button a document will be generated that includes both content as well as the output of any embedded R code chunks within the document. You can embed an R code chunk like this:

mf1<-function(a,b,eps=0.0005){
  f<-function(i){
    i^2-3
  }
  repeat{abs(b-a)->ab
  if(ab<eps){
    break
  }else{
    if(f(a)*f(b)==0){
      list("f(a)",f(a),"f(b)",f(b))
    }else{
      if(f(a)*f(b)>0){
        return("无解")
      }else{
        c<-(a+b)/2
        print(c)
        if(f(c)==0){
          return(c)
        }else{
          if(f(a)*f(c)>0){
            c->a
          }else{
            c->b
          }
        }
      }
    }
  }
}
list(a=a,"f(a)"=f(a),b=b,"f(b)"=f(b),"a-b"=a-b,root=(a+b)/2,"f(root)"=f((a+b)/2))
}
mf1(1,6,eps=10^(-10))

## [1] 3.5
## [1] 2.25
## [1] 1.625
## [1] 1.9375
## [1] 1.78125
## [1] 1.703125
## [1] 1.742188
## [1] 1.722656
## [1] 1.732422
## [1] 1.727539
## [1] 1.72998
## [1] 1.731201
## [1] 1.731812
## [1] 1.732117
## [1] 1.731964
## [1] 1.73204
## [1] 1.732079
## [1] 1.732059
## [1] 1.73205
## [1] 1.732055
## [1] 1.732052
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051
## [1] 1.732051

## $a
## [1] 1.732051
## 
## $`f(a)`
## [1] -1.509637e-11
## 
## $b
## [1] 1.732051
## 
## $`f(b)`
## [1] 2.3695e-10
## 
## $`a-b`
## [1] -7.275958e-11
## 
## $root
## [1] 1.732051
## 
## $`f(root)`
## [1] 1.109268e-10

#来源
fzero<-function(f,a,b,eps=1e-5){
  if(f(a)*f(b)>0){
    list(fail="finding root is fail!")
  }else{
    repeat{
      if(abs(b-a)<eps){
        break
        }else{
          x<-(a+b)/2
          if(f(a)*f(x)<0) b<-x 
                    else a<-x}}
             list(root=(a+b)/2,fun=f(x))}}
f<-function(x) x^3-x-1
fzero(f,1,2,1e-6)

## $root
## [1] 1.324718
## 
## $fun
## [1] -1.857576e-06

You can also embed plots, for example:

Note that the echo = FALSE parameter was added to the code chunk to prevent printing of the R code that generated the plot.